d4fa1fd353 added tracking to changes
from *comments* (as well as a few hacks around authorship transfer),
however it missed two things:
First, it set the `change-author` during comments handling only, so
changes from the `PullRequest` hook e.g. open, synchronise, close,
edit, don't get attributed to their actual source, and instead just
fall back to uid(1). This is easy enough to fix as the `sender` is
always provided, that can be resolved to a partner which is then set
as the author of whatever changes happen.
Second, I actually missed one of the message hooks: there's both
`_message_log` and `_message_log_batch` and they don't call one
another, so both have to be overridden in order for tracking to be
consistent. In this case, specifically, the *creation* of a tracked
object goes through `_message_log_batch` (since that's a very generic
message and so works on every tracked object created during the
transaction... even though batch has a message per record anyway...)
while *updates* go through `_message_log`.
Fixes#895
f3a0a5c27c